This invention relates generally to techniques for forming semiconductor devices such as field emission displays and particularly, in one embodiment, to techniques for sharpening the emitters of field emission displays.
There is currently considerable interest in field emission displays as an alternative to liquid crystal displays for use in electronic devices, such as laptop computers. Field emission displays offer many advantages. However, large displays must be formed on large supporting structures. Conventional silicon wafers have some drawbacks as the supporting structure for large field emission displays. The drawbacks include the fact that current wafer sizes may not be sufficiently large to accommodate these applications. Moreover, a wafer, of the size necessary to form a large field emission display on a single wafer, would be relatively expensive.
Therefore, there is some interest in developing field emission displays formed on structures called baseplates other than silicon wafers. One highly advantageous structure uses an amorphous silicon layer atop a glass supporting structure. These baseplates have a number of advantages including the ability to form large displays at reasonable cost. On the other hand, these structures are not amenable to high temperature processing normally associated with silicon wafer processing. By high temperature processing, it is intended to refer to the normal diffusion processes which take place temperatures on the order of 700.degree. C. and higher.
For example, one problem that arises in using non-silicon wafer based support structures is that conventionally, the emitters are formed using high temperature oxide steps. One example would be that conventionally high temperatures may be utilized to sharpen the emitter tips so as to increase the emission efficiency of those devices. However, oxidizing processes conventionally require temperatures on the order of 900.degree. C. and thus, are not suitable for some silicon-glass supporting structures.
One advantageous material for forming baseplates is soda-lime glass. However, soda-lime glass includes alkaline constituents, which may diffuse into and contaminate a silicon layer deposited on the glass baseplate. A number of techniques have been developed to attempt to isolate the silicon layer from the underlying soda-lime glass to prevent contamination from the alkaline constituents. One such technique is to use an intermediate barrier layer.
Thus, there is a need for a way of making structures such as glass structures that may be adversely affected by contaminants in the glass structures.